Interpretive Summary: Forages and by-products are important materials for the feeding of ruminants (i.e, cattle). As such, considerable effort is expended on the determination of their composition. Pyrolysis (PY)is a procedure in which materials are heated in an inert atmosphere (No oxygen present). The heat causes the material to break down into simpler compounds whose composition depends on the starting materials. When connected to instruments capable of separating the compounds produced (gas/chromatography or GC) and then to an instrument capable of identifying the separated compounds (mass/spectrometry or MS), the procedure can be used to rapidly provide information on the composition of various materials. Research has demonstrated that PY/GC/MS can provide detailed information on the composition of many of the components of forages and by-products. The information provided has been shown to be useful in determining the basis for wet chemical procedures commonly used to obtain compositional data, in differentiating subtle differences in composition between varieties of the same plant species, and in comparing the overall composition of one material to another. While PY/GC/MS is extremely useful for determining many of the components of forages and by-products, it does not perform well for proteins, one of the most important components of such materials. The reason for this has not been determined and further research is needed. Although is it possible that some protein derived compounds are simply not being identified, it appears that there is a more fundamental problem. Finally, it is believed that PY/GC/MS can be a tremendous tool for the determination of forage and by-product composition which has been largely ignored by animal nutritionists and forage researchers.

Technical Abstract:
Forages and by-products are important materials for the feeding of ruminants. As such, considerable effort is expended on the determination of their composition. Unfortunately, most of the procedures used to date are empirical in nature and make such determinations difficult at best. Pyrolysis/gas/chromatography/mass/spectrometry (PY/GC/MS), on the other hand, is simple to carry out and generates no wastes, while being capable of simultaneously providing information on the composition of many or all the constituents in the material in question. Research has demonstrated that PY/GC/MS can provide detailed information on the composition of lignin, tannins and the carbohydrate fractions of forages and by-products. The information provided has been shown to be useful in determining the basis for wet chemical procedures (i.e., what exactly does a procedure for lignin content determine), in differentiating subtle differences in composition between varieties of the same plant species, and in comparing the overall composition of one material to another. PY/GC/MS is extremely useful for the study of lignin and carbohydrates, but, at present, is less useful for the study of proteins. While results have shown that the determination of nitrogen containing materials by PY/GC/MS is not a problem per se, for proteins, in particular, relatively few markers and in relatively low yields are reported as compared to lignin and carbohydrates. Although is it possible that some protein based fragments are simply not being identified, it appears that there is a more fundamental problem. Finally, it is believed that PY/GC/MS can be a tremendous tool for the determination of forage and by-product composition which has been largely ignored by animal nutritionists and forage researchers.